N0.12C5. SYNOPSIS OF THE NAIADES— SIMPSON. 791 



ridges curved up behind; posterior ridge feebly developed; epidermis 

 brownish or blackish, and often painted with a few faint rays on the 

 earlier shell which are disposed to break into squarish spots; hinge 

 and teeth strong; secondary lateral in right valve well developed; 

 beak cavities deep, compressed; muscle scars deep. Animal with all 

 four gills used as a marsupium throughout, filled with pink ova; gills 

 large, inner only slightly the larger, free the greater part of their 

 length; anal opening crenulate or papillose. 



t QUADRULA BURSA-PASTORIS B. H. Wright. 



* Unio hursa-pastoris B. H. Wright, Nautilus., IX, 1896, p. 133, pi. in. 

 Clinch and Powell rivers; A^irginia and Tennessee. 



t QUADRULA KIRTLANDIANA Lea. 



* Unio hirtlandianus Lea, Tr. Am. Phil. Soc, V, 1834, p. 98, pi. xiv, fig. 41 ; * Obs., 



1, 1834, p. 210, pi. XIV, fig. 41.— * Ferussac, Guer. Mag., 1835, p. 29.— * Han- 

 ley, Biv. Shells, 1843, p. 203, pi. xxiii, fig. 27.—'* Catlow and Eeeve, Conch. 

 Norn., 1845, p. 60.— * Conrad, Pr.Ac. N. Sci. Phila., VI, 1853, p. 251.— TRUS- 

 TER, Conch. Cab., 1856, p. 168, pi. xlix, figs. 2, 3; 1861, p. '214, pi. lxxi, 

 fig. 1.— *H. and A. Adams, Gen. Eec. Moll., II, 1857, p. 492. — *Sowerby, 

 Conch. Icon., XVI, 1868, pi. Lxxvii, fig. 402.— *B, H. Wright, Check List, 

 1888.— * Pjetel, Conch. Sam., Ill, 1890, p. 156. 



* Margarita (Unio) Mrtlandianus Lea, Syn., 1836, p. 34; 1838, p. 23. 



* Margaron ( Unio) Mrtlandianus Lea, Syn., 1852, p. 35 ; 1870, p. 56. 

 " Unio kirUandianus Hanley, Test. Moll., 1842, p. 203. ' 



t QUADRULA KIRTLANDIANA var. MINOR Simpson.^ 



Ohio, Cumberland, and Tennessee river systems; southwest to 

 Arkansas; north to Wisconsin?; east through southern Michigan. 



t QUADRULA SUBROTUNDA Lea.« 



" Unio suhroiundus Lea, Tr. Am. Phil. Soc, IV, 1831, p. 117, pi. xviii, fig. 45; *0b8., 

 I, 1834, p. 127, pi. XVIII, fig. 45.—* Hanley, Test. Moll., 1842, p. 203 ; * Biv. 

 Shells, 1843, p. 203, pi. xx, fig. 58.—* Catlow and Eeeve, Conch. Norn., 1845, 

 p. 64.— * II. and A. Adams, Gen. Eec. Moll., II, 1857, p. 492.— *?Chenu, 111. 



1 A typographical error no doubt. There is a Unio MrMandianus recently named 

 by Wright. 



"A form is found in the Tennessee drainage which comes nearest, it seems to me, 

 to the I'irilandianus of Lea, but is much smaller and more delicate, and is not so 

 strongly colored. Mr. Wetherby believes this to be a form of the nearly allied 

 suhrotundus, but it seems to me too much compressed for that. Dr. Sterk; ja of the 

 opinion that the two species should be united. While there are specir^ens which 

 can hardly be determined, it seems to me that in the main the two are distinct. 

 The small form may be called variety minor. 



^ The name subrotunda was used by Eafinesque in 1820 for some species of Naiad, 

 probably a member of the Cir cuius group which I can not determine, and placed in 

 the genus Ohliquaria by him. Conrad afterwards, in 1834, placed what he supposed 

 was this species in the genus Unio. Lea applied the name suhrotundus to his species 

 in 1831, and being the first to use it for that genus, I think it will have to stand, 

 and Conrad's name become a synonym. 



